Cimetidine-induced prolactin (PRL)secretion is mediated via the 5-HT2A mechanism. Atypical antipsychotic drug w/5-HT2A antagonism, will block cimetidine induced PRL secretion in patients w/schizophrenia. Cyproheptadine, a 5-HT2A/2C receptor antagonist w/antihistamine properties, will block cimetidine-induce PRL secrection in normal controls. The cimetidine- induced PRL response is blunted in patients w/schizophrenia compared to normal controls.